Universal Irrigation Controller Power Supply

ABSTRACT

Described herein are systems, methods and apparatuses for providing power to an irrigation controller. In one implementation, an apparatus comprises an alternating current (AC) to direct current (DC) voltage converter configured to convert an input AC voltage into a DC voltage. An AC voltage generator is coupled to the AC to DC voltage converter, wherein the AC voltage generator is configured to generate an output AC voltage using the DC voltage. The AC voltage generator is further coupled to the irrigation controller, and the AC voltage generator is configured to supply the output AC voltage to the irrigation controller.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to providing power to irrigationcontrollers, and more specifically to conversion of input power signalsfor use by irrigation controllers.

2. Discussion of the Related Art

Irrigation controllers are typically used to control and actuate valvescontrolling the flow of water therethrough. Irrigation controllers areoften required to be connected to an alternating current (AC) powersource. Such controllers often use an input AC power signal at least togenerate an output AC power signal used in actuating the valves. Forexample, a 110/120 or 220/240 volts AC (VAC) (herein generally referredto as 120 and 240 VAC respectively) input AC voltage source istraditionally stepped down or converted into a 24 VAC supply using aconventional step-down transformer. The 24 VAC supply provides suitablepower for actuating the various valves controlled by the irrigationcontroller.

However, there are a number of issues in using the above describedstep-down power supply. The step-down transformer is constructed tostep-down the voltage level of the input voltage (e.g., a primaryvoltage) to produce a voltage at the output of the transformer (e.g., asecondary voltage). Thus, a first problem with the step-down transformerpower supply is that when the voltage level of the power source varies,the input voltage varies, and the step-down transformer produces theoutput voltage to follow the input voltage. Therefore, the outputvoltage level will vary in proportion to the input voltage level. Thiscan result in too much or too little operating voltage at the valvesolenoid.

Additionally, such transformers used in step-down power supplies must bedesigned to accommodate for such variations and are typically not veryefficient. In some embodiments, these transformers cause excessive heatunder load and significant power consumption due to core losses, evenwhen no valves are operating. It is noted that recent governmentalregulations are beginning to mandate higher requirements for “standby”power efficiency. These regulations are hard to meet with a conventionalstep-down transformer.

Another issue with conventional step-down power supplies is that thetransformers used are both heavy and expensive. This weight results inadded shipping costs and thicker support components. A big additionalcost is incurred by the company for the engineering time and activitiesneeded to select and certify new suppliers. Additionally, continuousgrowth in the global prices for copper increases power transformers'prices. For example, it is believed that over 50% of a transformer'sprice is derived from copper material costs. This situation hinders longterm estimations of cost reductions and future part consolidationprograms.

Finally, in order to accommodate the different electrical standards(e.g., 120 and 240 VAC), found in different countries, several differentversions of the traditional step-down power supplies and irrigationcontrollers must be produced using different types of transformers. Forexample, the transformers must be able to handle the specific voltage(e.g., 120 or 240 VAC) and the specific frequency (e.g., 50 or 60 Hz),as well as normal variations thereof, of the country in which thecontroller will be used.

SUMMARY OF THE INVENTION

Several embodiments of the invention advantageously address the needsabove as well as other needs by providing methods, systems andapparatuses for providing power for use by an irrigation controller.

In one embodiment, an apparatus is presented comprising an alternatingcurrent (AC) to direct current (DC) voltage converter configured toconvert an input AC voltage into a DC voltage. An AC voltage generatoris coupled to the AC to DC voltage converter, and the AC voltagegenerator is configured to generate an output AC voltage using the DCvoltage. The AC voltage generator is coupled to the irrigationcontroller, and the AC voltage generator is further configured to supplythe output AC voltage to the irrigation controller.

In another embodiment, a method for powering an irrigation controller ispresented comprising converting an input alternating current (AC)voltage signal into a direct current (DC) voltage signal and generatingan output AC voltage signal using the DC voltage signal. The outputvoltage signal is configured to power the irrigation controller and theoutput AC voltage signal is supplied to the irrigation controller.

In yet another embodiment, a power supply comprises an input configuredto receive an input alternating current (AC) voltage ranging from 85volts AC to 260 volts AC. The power supply includes an output configuredto couple to an irrigation device, and a circuit to generate an outputAC voltage. The output AC voltage powers the irrigation device and theoutput AC voltage is substantially constant regardless of whether theinput AC voltage varies in at least one of frequency and voltage.

In yet another embodiment, a method is presented comprising receiving aninput alternating current (AC) voltage having a voltage level rangingbetween 85 to 260 volts AC and generating, based at least in part on theinput AC voltage, a substantially constant output AC voltage configuredto be used by an irrigation controller regardless of whether the inputAC voltage varies in at least one of frequency and voltage.

In yet another embodiment, an irrigation controller power supply ispresented, comprising an input adapted to receive an alternating current(AC) signal. The power supply further comprises an AC to direct current(DC) converter coupled to the input, wherein the AC to DC converter isadapted to output a DC signal derived from the AC signal. An ACgenerator adapted to generate an output AC signal using the DC signal isprovided and a control output is coupled to the AC generator, whereinthe control output is adapted to couple to an irrigation control device.The control output is further adapted to drive the irrigation controldevice with the output AC signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of severalembodiments of the present invention will be more apparent from thefollowing more particular description thereof, presented in conjunctionwith the following drawings.

FIG. 1 is a block diagram of a power supply for providing power for useby an irrigation controller according to one embodiment;

FIG. 2 is a flow diagram of the steps involved in a method for providingpower for use by an irrigation controller according to one embodiment;

FIG. 3 is a block diagram of an AC to DC voltage converter according toone embodiment of FIG. 1;

FIG. 4 is a block diagram of an AC voltage generator according to oneembodiment of FIG. 1;

FIG. 5 is a block diagram of a power supply for providing power for useby an irrigation controller according to one embodiment;

FIG. 6 is a block diagram of a power supply for providing power for useby an irrigation controller according to one embodiment;

FIG. 7 is a flow diagram of the steps performed in a method of providingpower for use by an irrigation controller according to one embodiment;

FIG. 8 is a block diagram of a power supply for providing power for useby an irrigation controller according to one embodiment;

FIG. 9 is a diagram illustrating various waveforms to show the detectionof unstable operating conditions according to one embodiment;

FIG. 10 is a flow diagram of the steps performed in a method ofproviding power for use by an irrigation controller according to oneembodiment;

FIG. 11 is flow diagram of the steps performed in a start-up method forproviding power for use by an irrigation controller according to oneembodiment;

FIG. 12 is a block diagram of components of the AC voltage generatoraccording to one embodiment;

FIG. 13 is a diagram illustrating various waveforms and steps performedto determine a frequency for an output voltage for use by an irrigationcontroller according to one embodiment; and

FIG. 14 is a high level circuit diagram illustrating one embodiment ofthe power supply of FIG. 1.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings. Skilled artisans willappreciate that elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale. For example,the dimensions of some of the elements in the figures may be exaggeratedrelative to other elements to help to improve understanding of variousembodiments of the present invention. Also, common but well-understoodelements that are useful or necessary in a commercially feasibleembodiment are often not depicted in order to facilitate a lessobstructed view of these various embodiments of the present invention.

DETAILED DESCRIPTION

The following description is not to be taken in a limiting sense, but ismade merely for the purpose of describing the general principles ofexemplary embodiments. The scope of the invention should be determinedwith reference to the claims.

Several embodiments of present invention set forth an apparatus, systemand method for use by an irrigation device. In a specific embodiment, anapparatus, system and method are provided for converting an alternatingcurrent (AC) voltage ranging from 85 to 260 volts AC into a directcurrent (DC) voltage, wherein the DC voltage is used to create an ACvoltage adapted for use by an irrigation control device.

Referring first to FIG. 1, a block diagram of a power supply forproviding power for use by an irrigation controller according to oneembodiment is illustrated. System 100 includes an input AC voltagesignal 102, a power supply 104, and an irrigation controller 106. Thepower supply 104 includes an AC to DC voltage converter 108 coupled toan AC voltage generator 110. It is noted that the AC to DC voltageconverter 108 and the AC voltage generator 110 may each be referred toas a circuit or circuitry.

According to several embodiments, a power supply housing 112 enclosesthe power supply 104. The power supply housing 112 is configured toreceive, from an AC power source, the input AC voltage signal 102 foruse by the power supply 104. The input AC voltage signal 102 is directedto the AC to DC voltage converter 108 in order to convert the input ACvoltage to a DC voltage signal 114. The DC voltage signal 114 is thenused by the AC voltage generator 110 to generate an output AC voltage116.

The power supply housing 112 may comprise metallic terminals wherein anexternal two or three wire AC power source is coupled to the powersupply housing 112, which in turn is directed to the power supply 104.In some embodiments, the AC to DC voltage converter 108 converts theinput AC voltage signal 102 by rectifying and filtering the voltagesignal to create a substantially constant DC voltage signal 114, e.g.using a switching power supply. The AC voltage generator 110 thengenerates an output AC voltage 116 using the DC voltage signal 114 toamplify a periodic signal created independent from the input AC voltage.Thus, the power supply 104 is configured to provide power for use by theirrigation controller 106 by receiving an input AC voltage signal 102and generating, based at least in part on the input AC voltage signal102, the output AC voltage 116.

In some embodiments, the power supply 104, and thus, the AC to DCvoltage converter 108, is configured to receive an input AC voltagesignal 102 having a voltage level at least within a predetermined range.By way of example, the AC to DC voltage converter 108 receives anyuniversally available power source comprising the input AC voltagesignal 102. According to several embodiments, the AC to DC voltageconverter converts the input AC voltage signal 102 into the DC voltagesignal 114 regardless of the voltage level of the universally availablepower source; as long as it is within the predetermined range of, forexample, 85 to 260 VAC. Thus, in one form, the power supply 104 may beused universally, and different versions are not needed for differentcountries.

According to several embodiments, the power supply 104 is configured toconvert the input AC voltage signal 102 to substantially the equivalentDC voltage signal 114 for all different voltage levels of the AC powersource. Thus, in some embodiments, if the voltage level or frequency ofthe input AC voltage signal 102 varies over time, the AC to DC voltageconverter 108 is configured to continue generating a substantiallyconstant DC voltage signal 114. According to some embodiments, the AC toDC voltage converter is configured to provide a substantially constantDC voltage signal 114 of around 48 V, regardless of the voltage leveland frequency, or any variation therein, of the input AC voltage signal102. In some embodiments, implementing the above described switchingtype power supply to provide power for use by the irrigation controller,instead of the traditional step-down transformer type power supply,provides benefits such as accepting a universal power source andrequiring smaller, less expensive and more efficient components.

Most countries around the world provide electric power configured as oneof a plurality of different standards, for example, of 110 VAC or 220VAC and typically with a frequency of 60 Hz or 50 Hz respectfully.Additionally, the electricity received at a customer's home, forexample, may vary from the standard in either voltage and/or frequency.

Thus, in order to address the variations among different country'selectricity standards and variations in electricity actually received atthe customer's site, the power supply housing 112 is configured, in someembodiments, to receive any universal AC power source. According toseveral embodiments, the power supply 104 is configured use theuniversal AC power source, having a voltage level ranging from 85 to 260VAC and a frequency ranging from below 50 Hz to above 60 Hz, to generatean acceptable output AC voltage 116 (e.g., 24 VAC) for use by theirrigation controller. Furthermore, in one form, the AC voltagegenerator 110 is further configured to generate the output AC voltage116 at a substantially constant voltage and a substantially constantfrequency, regardless of whether the input AC voltage signal 102 variesin at least one of frequency and voltage level.

According to some embodiments, the input AC voltage signal 102 variesover time and between different sites up to a 20% increase and/ordecrease from the standard level. In one embodiment, when the input ACvoltage signal 102 varies in voltage level from 85 VAC to 260 VAC and infrequency from 45-75 Hz, the AC voltage generator 110 generates asubstantially constant output AC voltage 116, e.g., at 24 VAC and 50 Hz,used by the irrigation controller 106.

In another embodiment, the AC voltage generator 110 uses the DC voltagesignal 114, e.g., 48 V, to generate the output AC voltage 116 of 24 VACat 50 Hz for use by the irrigation controller 106. In some embodiments,the AC voltage generator 110 provides an output AC voltage 116 to theirrigation controller 106 which is used to control one or more waterflow control devices, such as, mechanically or electrically actuatedvalves which control the flow of water to one or more sprinkler devices.For example, many standard water flow control devices operate with 24VAC. According to some embodiments, the irrigation controller 106 alsoderives operation power (e.g., DC voltage/current) from the power supply104.

In some embodiments, the irrigation controller 106 is external to thepower supply housing 112 and is supplied the output AC voltage 116 via awire or a cable. In some embodiments, the irrigation controller 106 isinternal to, or also enclosed within, the power supply housing 112. Or,in some embodiments, the power supply 104 is enclosed within a housingof the irrigation controller 106.

Referring next to FIG. 2, a flow diagram of the steps involved in amethod for providing power used by an irrigation controller according toone embodiment is illustrated. According to several embodiments, method200 begins by converting an input AC voltage to a DC voltage (step 202).In one embodiment, the conversion is performed by the power supply 104of FIG. 1, and more specifically the AC to DC voltage converter 108.Next, the method continues with generating an output AC voltage usingthe DC voltage (step 204). For example, this step is performed by the ACvoltage generator 110 of FIG. 1. Next, the method continues withsupplying the output AC voltage to the irrigation controller (step 206).

By way of example, the AC to DC voltage converter 108 is configured tofilter and rectify the input AC voltage, e.g., of 110 VAC at 60 Hz, forconversion into a DC voltage of 48 V. The DC voltage of 48 V, forexample, is then used by the AC voltage generator 110 to amplify aperiodic signal having a predetermined frequency. According to severalembodiments, the AC voltage generator 110 generates and amplifies apulse width modulated signal with a frequency of 60 Hz in order togenerate the output AC voltage of 24 VAC at 60 Hz.

According to several embodiments, water flow control devices controlledby irrigation controllers are configured to use a power supply of 24 VACat or around either 50 Hz or 60 Hz, depending on the electricitystandard of the country where the irrigation controller is being used.In one embodiment, the input AC voltage signal 102 received at the powersupply 104 is 210 VAC at 51 Hz and, accordingly, the output AC voltage116 generated by method 200 is substantially equal to 24 VAC at 50 Hz.Additionally, if the input AC voltage signal 102 received at the powersupply 104 varies over time from 210 to 230 VAC and 51 to 49 Hz, the ACvoltage generator 110 generates the output AC voltage 116 to besubstantially equal to 24 VAC at 50 Hz.

Furthermore, the power supply 104 according to the embodiment above isalso configured to receive an input AC voltage of 115 VAC at 60 Hz, andin turn, the generated output AC voltage 116 is substantially equal to24 VAC at 60 Hz. Thus, as described above, the power supply 104 isconfigured to convert the input AC voltage signal 102 having a voltagelevel ranging from 85 to 260 VAC and a frequency level around 50 Hz or60 Hz. Further details are provided below in regards to the performanceof steps 202 and 204.

Referring next to FIG. 3, a block diagram of an AC to DC voltageconverter according to one embodiment of FIG. 1 is illustrated. The ACto DC voltage converter 108 includes a rectifier 320, a power factorcorrection module 322 and a DC to DC converter 324.

As illustrated, an input AC voltage signal 102 is coupled to the inputof the rectifier 320, and the output of the rectifier 320 is coupled tothe input of the power factor correction module 322. The output of thepower factor correction module 322 is coupled to the DC to DC converter324, and the DC to DC converter outputs a DC voltage signal 114.

The rectifier 320 at least rectifies the input AC voltage signal 102 tocreate a DC voltage signal 114 using, for example, a diode bridge. Insome variations, the rectifier 320 also includes an electromagneticinterference (EMI) filter in addition to a diode bridge in order torectify and filter the input AC voltage signal 102 to create a DCvoltage signal 114.

As is generally understood, when designing power supplies, specificgovernmental regulations require the power supply to comply with avariety of safety and quality standards. For example, in a systemcomprising small enclosure size and switch mode circuitry, compliance ofgovernmental standards for radiated and conducted electromagneticinterference (EMI) presents one of the more significant challenges. Somecompliance standards require the EMI radiation to be below apredetermined threshold. However, the regulations imposed on powersupplies differ depending on the amount of power being supplied. In someembodiments, the power supply 104 described in FIG. 1 is configured tosupply less than 70 watts (W) of power, and accordingly, the radiationrequirements are less stringent. However, in some embodiments,additional benefits may be achieved by reducing radiation emitted fromthe power supply 104 even though not required for compliance togovernment standards.

Thus, FIG. 3 depicts the input AC voltage 102 being rectified by therectifier 320 and passed to the power factor correction module 322. Thepower factor correction module 322 corrects the power factor of theinput circuitry to improve efficiency. In some embodiments, the powerfactor correction module 322 also includes circuitry to suppressemissions. In other embodiments, no power factor correction module 322is provided and the DC voltage having been rectified is supplieddirectly to the DC to DC converter 324.

Although power factor correction (PFC) may not be mandatory whensupplying 70 W or less, in some embodiments, the power factor correctionmodule 322 is incorporated into the AC voltage converter 112.Incorporating PFC, in such embodiments, provides additional benefits,such as simplifying the input AC voltage signal 102 circuitry, improvingutilization of AC mains circuits, reducing distortion and noise on ACmains, simplifying design and reducing the size of DC to DC converter324, and requiring less storage capacitance to reduce power-on surges.In some embodiments, the power factor correction module 322 is a singlestage power factor controller, which accordingly, provides a goodcompromise between size, cost, complexity and efficiency factors. It isunderstood that the term AC mains refers to the source of the input ACvoltage signal 102.

In some variations, the power factor correction module 322 is anaverage-current-feedback boost converter that supplies a direct currentto the DC to DC converter 324. In some embodiments, the DC to DCconverter 324 also provides safety isolation and bears most of theburden of the regulation. Considerations such as size, weight, thermallevels and efficiency may influence the choice of using a switch modepower supply for the AC to DC conversion circuitry. Additionally, insome embodiments, the pre-regulation provided by the power factorcorrection module 322 permits the use of smaller magnetic components inthe DC to DC converter 324. Furthermore, in some embodiments, the powerfactor correction module 322 also benefits the efficiency of the powersupply 104 wherein the DC to DC converter 324 provides power to the ACvoltage generator 110 shown in FIG. 1.

Referring next to FIG. 4, a block diagram of an AC voltage generatoraccording to one embodiment of FIG. 1 is illustrated. The AC voltagegenerator 110 includes a frequency generator 442, an amplifier 444, anisolator 446 and a filter 448. The AC voltage generator 110 isconfigured to receive a frequency signal 410 and a DC voltage signal 114in order to provide an output AC voltage 116 for use by an irrigationcontroller.

According to several embodiments, the frequency generator 442 dictatesthe frequency of the output AC voltage 116, which, in some embodiments,corresponds to the frequency signal 410. Additionally, in someembodiments, the frequency signal 410 is a signal that corresponds tothe frequency of the input AC voltage signal 102 (as shown at least inFIGS. 1-3). In some embodiments, the frequency signal 410 is only anindication when the input AC voltage signal 102 is stable enough for theAC voltage generator 110 to begin generating the output AC voltage 116.According to several embodiments, the DC voltage signal 114 suppliesoperational power to the frequency generator 442. In some embodiments,the DC voltage signal 114 is supplied to the frequency generator 442 toindicate whether or not the power supply is in a stable operation.

Accordingly, the frequency generator 442 generates a periodic signal 422using the frequency signal 410, and the periodic signal 422 is suppliedto the amplifier 444. The amplifier 444 in turn uses the DC voltagesignal 114 to amplify the periodic signal 422 to generate an amplifiedsignal 426. According to some embodiments, the amplified signal 426 isthe output AC voltage 116. That is, in some embodiments, the AC voltagegenerator 110 uses only the frequency generator 442 and the amplifier444 to generate the output AC voltage 116. According to severalembodiments, the AC voltage generator 110 also includes an isolator 446and a filter 448. Thus, the amplified signal 426 is optionally passedthrough the isolator 446 and/or the filter 448 prior to providing theoutput AC voltage 116 for use by an irrigation controller.

In one embodiment, the frequency signal 410 is from a crystal generatinga fixed frequency signal, and the frequency generator 442 is a digitalclock configured to output a periodic signal 422 at substantially thefixed frequency. In other embodiments, the frequency signal 410 is acombination of clock signals and/or a signal generated from a detectionmodule (e.g., a zero-crossing detector, discussed in further detailbelow) that detects the frequency of the input AC voltage signal 102.Thus, according to some embodiments, the frequency signal 410 indicates,to the frequency generator 442, at which frequency to generate theperiodic signal 422. In several embodiments, the frequency generator 442is a configurable pulse width modulator (PWM) and/or a microcontrollerconfigured to output a controlled periodic signal 422, such as a pulsewidth modulated signal or a sine wave at a frequency dictated by thefrequency signal 410.

According to several embodiments, the frequency generator 442 outputs apulse width modulated signal that corresponds to the frequency signal410 and/or the input AC voltage signal 102. For example, in oneembodiment, the input AC voltage signal 102 has a frequency at or around50 Hz±5% and thus the frequency signal 410 is a pulse signal (e.g., arising edge of a digital signal) occurring every 0.02 seconds ( 1/50Hz). Accordingly, the frequency generator 442 uses this frequency signal410 to generate a periodic signal 422 with a frequency substantiallyequal to 50 Hz.

Alternatively or additionally, in one embodiment, the input AC voltagesignal 102 has a frequency at or around 60 Hz±5%, and the frequencysignal 410 is a pulse signal occurring every 0.0167 seconds. Thus, thefrequency generator 442 generates a periodic signal 422 with a frequencysubstantially equal to 60 Hz. As described above, the periodic signal422 is supplied to the amplifier 444 for amplification.

According to several embodiments, the amplifier 444 is a digitalamplifier, e.g., a class D amplifier. In some embodiments, the amplifier444 is digitally controlled by the frequency generator 442. Theamplifier 444 produces an amplified signal 426 which, in someembodiments, is the output AC voltage 116. In other embodiments, theamplified signal 426 is first passed through the isolator 446 prior togenerating the output AC voltage 116.

In some embodiments, the isolator 446 provides protection to the ACvoltage generator 110 should a load be incorrectly coupled to the outputof the AC voltage generator 110. And, in some embodiments, the amplifiedsignal 426 is, additionally and/or alternatively, passed through thefilter 448 prior to generating the output AC voltage 116. The filter448, in some embodiments, provides a reduction in overallelectromagnetic emissions by the power supply 104, and may additionallyprovide a cleaner/sharper output AC voltage 116 to the irrigationcontroller.

Referring next to FIG. 5, a block diagram of a power supply according toone embodiment of FIG. 1 is illustrated. An irrigation device enclosure502 includes a power supply 104 and the irrigation controller 106. Thepower supply 104 includes an AC to DC voltage converter 108, an ACvoltage generator 110 and a monitor module 504.

According to several embodiments, the input AC voltage signal 102 issupplied to the power supply 104 and directed to the AC to DC voltageconverter 108 and the monitor module 504. In some embodiments, themonitor module 504 is also coupled to the AC to DC voltage converter 108and/or the AC voltage generator 110. As described in reference to FIG.1, the AC to DC voltage converter 108 is coupled to the AC voltagegenerator 110, and, the AC voltage generator 110 generates the output ACvoltage 116 for use by the irrigation controller 106 and/or otherattached devices.

As shown in FIG. 5, the power supply 104 and the irrigation controller106 are located within the irrigation device enclosure 502.Alternatively, in some embodiments, the power supply 104, or anycomponents thereof, e.g., the AC to DC voltage converter 108, the ACvoltage generator 110, and/or the monitor module 504, are external to,or located outside of the irrigation device enclosure 502.

According to several embodiments, the monitor module 504 monitors thepower supply 104 for specific operating conditions. In some embodiments,the monitor module 504 monitors the AC-DC voltage converter 108 and/orthe AC input voltage 102 to detect unstable operating conditions. Insome embodiments, the monitoring module 504 is configured to cause theAC voltage generator 110 to cease generating the output AC voltage 116upon detecting an unstable operating condition. According to someembodiments, upon detecting an unstable operating condition, the monitormodule 504 disables the amplifier 444 of the AC voltage generator 110 asshown in FIG. 4. In some embodiments, the monitoring module 504 isconfigured to cause the AC-DC voltage converter to cease producing theDC voltage output 114 upon detecting an unstable operating condition. Asis generally understood, an unstable operating condition may occur whenthere is a surge of current supplied to the irrigation device enclosure502 (e.g., across input terminals of the irrigation device enclosure502, not shown) and/or detected within the power supply 104 (e.g.,detecting an unstable current output from the AC to DC voltage converter108.) An unstable operating condition includes AC input voltage 102being too high or low or the frequency of AC input voltage 102 being toohigh or low. Other unstable operating conditions include excessivecurrent consumption, also known as overload, in the AC voltage generator110 or irrigation controller 116.

Referring next to FIG. 6, a block diagram of a power supply according toone embodiment of FIG. 5 is illustrated. A power supply 104, including afront end board 602 and a back end board 604, is illustrated forproviding power for use by an irrigation controller 106. The front endboard 602 includes the AC to DC voltage converter 108 and an ACzero-crossing detector 606. The back end board 604 includes a currentsensor 608 and the AC voltage generator 110.

According to several embodiments, an input AC voltage signal 102 issupplied to the front end board 602. The input AC voltage signal 102 isdirected to the AC to DC voltage converter 108 and the AC zero-crossingdetector 606. As described above, the AC to DC voltage converter 108receives the input AC voltage signal 102 and converts it to a DC voltagesignal 114 by, for example, rectifying and filtering the input ACvoltage signal 102. The front end board 602 is coupled to the back endboard 604, wherein the DC voltage signal 114 is supplied to the currentsensor 606 and the AC voltage generator 110.

In some embodiments, the AC zero-crossing detector 606 is used todetermine the frequency of the input AC voltage signal 102 by analyzingthe input AC voltage signal 102 to detect when the voltage level crosseszero volts (discussed in further detail below). In some embodiments, theAC zero-crossing detector 606 supplies a frequency signal 410 to the ACvoltage generator 110, as shown in FIG. 4, to indicate at whichfrequency the output AC voltage 116 should be generated. The currentsensor 608 is also coupled to the AC voltage generator 110 and to theirrigation controller 106. In some embodiments, the AC zero-crossingdetector 606 and/or the current sensor 608 are examples of the monitormodule 504 shown in FIG. 5.

In some embodiments, when the voltage and/or current of a power sourceis unstable for a certain amount of initial cycles (e.g., an initialthree cycles), the voltage and current at the initial power on cyclesmay exceed and/or fall below a limit that will harm or destroycomponents of the power supply 104 and/or irrigation controller 106.Thus, in some embodiments, the frequency signal 410 also indicates tothe AC voltage generator 110 when the input AC voltage 102 has reached astable operating condition, for example, the voltage level has crossedzero volts at least six times. Additionally, in some embodiments, thecurrent sensor 608 monitors the current and/or voltage level of the DCvoltage signal 114, and notifies the AC voltage generator 110 when ithas reached a predetermined level. Once the AC voltage generator 110 hasreceived proper indication via the AC zero-crossing detector 606 or thecurrent sensor 608, the AC voltage generator 110 will start generatingthe output AC voltage 116.

According to several embodiments, the current sensor 608 is used todetect unstable operating conditions after the AC voltage generator 110has begun generating the output AC voltage 116. In some embodiments, thecurrent sensor 608 analyzes the DC voltage signal 116 to determine whenthe voltage level and current level exceeds and/or falls below apredetermined threshold. For example, unstable voltage could be an inputof less than 85 volts or more than 260 volts. In another example, thecurrent threshold could be a maximum level, such as 5 amperes. In someembodiments, the current sensor 608 detects a power source input currentlevel. In some embodiments, the current sensor 608 determines if animproper load has been coupled to, or in place of, the irrigationcontroller 106. For example, when an improper voltage is coupled to theoutput of the back end board 604, the current sensor 608 detects aproblem and shuts down the AC voltage generator 110 and/or causes it tocease generating the output AC voltage 116.

According to some embodiments, the AC zero-crossing detector 606 islocated on the back end board 604; and, alternatively or additionally,the current sensor 608 is located on the front end board 602. Thus,systems presented depict example configurations, however, one skilled inthe art may implement a different configuration depending on size and/orspace considerations. It is understood that the front end board 602 andthe back end board 604 are provided by way of example. In someembodiments, all components are located on one board.

Referring next to FIG. 7, a flow diagram is shown of the steps performedin a method of providing power for use by an irrigation controlleraccording to another embodiment. In one embodiment, the method 700begins by receiving an input AC voltage ranging from 85 to 260 VAC (step702).

In one embodiment, the AC to DC voltage converter 108 of the powersupply 104 of FIG. 1 is configured to receive an input AC voltage 102ranging from 85 to 260 VAC. The AC to DC voltage converter 108 is alsoconfigured convert the input AC voltage 102 ranging from 85 to 260 VACto a DC voltage signal 114.

Next, the method 700 continues with generating an output AC voltagebased at least in part on the received input AC voltage (step 704). Forexample, the power supply 104 of FIG. 1 directs the DC voltage signal114, having been converted from the 85 to 260 VAC, to the AC voltagegenerator 110 to generate the output AC voltage 116. The method 700continues with providing power for use by an irrigation controller (step706). Thus, the power supply 104 of FIG. 1 is configured to couple to anirrigation controller 106, and the AC voltage generator 110 supplies the24 VAC to the irrigation controller.

In some embodiments, the power supply 104 implementing the method 700may be used universally to receive any AC power source providing aninput AC voltage ranging from 85 to 260 VAC at 50 or 60 Hz. By way ofexample, in one embodiment, the input AC voltage 102 having beenreceived is 120 VAC that varies over time from 115 to 125, and has afrequency of 60 Hz. As shown in method 700, the power supply 104generates an output AC voltage 116 of 24 VAC at 60 Hz. Thus, althoughthe input AC voltage 102 is used to generate the output AC voltage 116,the output AC voltage 116 is not dependent on the variations of theinput AC voltage 102.

Thus, unlike a traditional step down transformer based power supply, thepower supply 104 generates a stable output AC voltage 116 regardless ofvariations in the input AC voltage 102. Additionally, in a traditionalstep down power supply the circuitry required to receive a universalinput from 85 to 260 VAC requires very expensive and bulky components ascompared to required to implement the steps of a switching power supplysuch as method 700.

According to several embodiments, using method 700, the power supply 104is also configured to generate a substantially constant output ACvoltage 116 to the irrigation controller 106 with a frequency based onthe frequency of the input AC voltage 102. However, the frequency of theoutput AC voltage 116, although based on the input AC voltage 102, doesnot follow the variations in frequency because the AC voltage generator110 shown FIG. 1 subsequently generates the frequency at a substantiallyconstant rate. In some embodiments, the power supply 104 generates theoutput AC voltage 116 to have a frequency being one of 50 Hz when a theinput AC voltage frequency is within a first frequency range (e.g., lessthan 54.5 Hz) and 60 Hz when the frequency of the input AC voltage iswithin a second frequency range (e.g., 54.5 Hz or higher).

Referring next to FIG. 8, a block diagram of a power supply forproviding power for use by an irrigation controller according to anotherembodiment is illustrated. An irrigation controller housing 802 includesa power supply 104 coupled to an irrigation controller 106. Theirrigation controller includes a plurality of control output terminals804 and 806. According to several embodiments, the control outputterminals 804 and 806 are coupled to a plurality of water flow controldevices 808 and 810, e.g., solenoid actuated valve terminals, locatedoutside of the irrigation controller housing 802. In other embodiments,the power supply 104 is located outside the irrigation controllerhousing 802 and is further coupled to the irrigation controller 106 viawires or cables.

According to several embodiments, the input AC voltage signal 102 issupplied to the power supply 104, wherein the input AC voltage signal102 is converted to a DC voltage signal. The DC voltage signal 114 isused at least in part to generate an output AC voltage 116 for use bythe irrigation controller 106. In some embodiments, the DC voltagesignal 114 is also supplied directly to the irrigation controller 106.Additionally and/or alternatively, the output AC voltage 116 is used bythe irrigation controller 106, e.g., switched to the appropriate outputterminal/s 804, 806 to actuate the appropriate water flow controldevices 808 and 810 to provide watering according to a stored wateringschedule. In some embodiments, the power supply 104 may provide powerfor use by control devices controlling low voltage devices other thanwater flow control devices, such as, lighting control devices, pool pumpcontrol devices, etc.

Referring next to FIG. 9, a diagram illustrating various waveforms toshow the detection of unstable operating conditions according to oneembodiment is illustrated. According to several embodiments, an overcurrent detection implementation is illustrated with an enable signal990, a pulse width modulated (PWM) output signal 992 and an AC outputsignal 994.

By way of example, in one embodiment, the enable signal 990 is high,e.g., a digital 1, when the system is in a stable operating condition.In this case, the enable signal 990 is low, e.g., a digital 0, when thesystem is in an unstable operating condition. Thus, in some embodiments,referring back to FIG. 4, the frequency generator 442 continues togenerate a periodic signal, as illustrated by the PWM output signal 992,as long as the enable signal 990 remains high. In some embodiments, theenable signal 990 indicates to the amplifier 444 that the system isoperating in a stable condition, and therefore, the amplifier 444continues amplifying the periodic signal 422 generated by the frequencygenerator 442.

In one embodiment, referring back to FIG. 5, the monitor module 504detects when the AC output signal 994 exceeds the threshold 996 forthree consecutive cycles. Thus, when the AC output signal 994 exceedsthe threshold 996 for only two consecutive cycles, the AC voltagegenerator 442 continues generating the output AC voltage 116 shown inthe AC output signal 994. As is generally understood, when a powersource is initially turned on, there is a normal in rush of energy.Thus, after only two cycles, the power supply 104 recognizes the ACoutput signal 994 is higher than normal due to the in rush of energy.

Typically the high in rush of energy will settle down after the thirdcycle. However, when the AC output signal 994 exceeds the threshold 996for three consecutive cycles, the power supply 104 recognizes this as anunstable operating condition. In some embodiments, at this point, e.g.,a disable point 998, the monitor module 504 pulls the enable signal 990low. A low enable signal 990 disables the AC voltage generator 110 andthe power supply 104 ceases generating the output AC voltage 116; asseen by the termination of AC output signal 994. In some variations, theenable signal 990 enables the AC voltage generator 110 comprising thefrequency generator 442 and amplifier 444. For example, referring backto FIGS. 5 and 6, the monitor module 504, such as a current sensor 608and/or a AC zero-crossing detector 606, detects when the output ACvoltage 116 has exceeded a voltage and/or current threshold 996 andsupplies the enable signal 990 only upon detecting a stable operatingcondition.

Referring next to FIG. 10, a flow diagram of the steps performed in amethod of providing power for use by an irrigation controller accordingto one embodiment. Method 1000 begins with determining if the powersupply is ready to begin generating power (step 1010). In someembodiments, as shown in FIG. 6, the determination is made by thecurrent sensor 608 that the power supply 104 is ready by monitoring theDC voltage signal 114. The current sensor 608 monitors the DC voltagesignal 114, having been converted from AC to DC voltage converter 108,to determine when the DC voltage signal 114 exceeds a pre-determinedvoltage threshold.

Additionally and/or alternatively, the determination is made by the ACzero-crossing detector 606 that the power supply 104 is ready bydetecting a pre-defined number of consecutive zero-crossings by theinput AC voltage 102. As discussed above, often when a voltage isapplied, during the initial coupling there may be a surge on voltage orcurrent, wherein attempting to convert the high voltage may damage ordestroy components of and/or attached to the power supply 104. Thus, ifthe power supply 104 delays generating a voltage and/or amplifying asignal, for at least the first few cycles after powering on, then thepower supply 104 may avoid damaging components. Thus, in someembodiments, determining the power supply 104 is ready is determined bycounting, for example, three zero-crossings by the input AC voltage 102.

Accordingly, when determining the power supply is not ready to begingenerating power, the power amplifier remains disabled. In someembodiments, the monitor module 504, the current sensor 608 or the ACzero-crossing detector 606 detects that the power supply 104 is in anunstable operating condition, and thus, sends a disable signal to, forexample, the amplifier 444 of FIG. 4 until the power supply 104 isready.

Next the method continues with determining a line frequency of the inputAC voltage based on the AC zero-crossing signal (step 1014). In someembodiments, the determination of the line frequency is made by the ACzero-crossing detector 606. In this case, the input AC voltage 102 issupplied to the AC zero-crossing detector 606, wherein the time betweenzero crossings of the input AC voltage 102 is recognized by the ACzero-crossing detector 606 converted into a frequency signal 410. Insome embodiments, the AC voltage generator 110 may receive zero-crossingsignals from the AC zero-crossing detector 606; wherein, any methodknown to one skilled in the art may be used to determine the frequencyof the input AC voltage using the zero-crossing signals (e.g., using ahalf cycle, a full cycle and/or an average of multiple cycles). Thus, insome variations, the output AC voltage 116 frequency is dependent on theline frequency of the input AC voltage, for example, wherein the outputAC voltage 116 frequency is chosen to be 50 Hz when the input AC voltagefrequency is less than 54 Hz, and is chosen to be 60 Hz when the inputAC voltage frequency is greater than or equal to 54 Hz.

The method continues with generating a PWM signal to be amplifiedaccording with the line frequency (step 1016). The PWM signal is aseries of pulses, the width of which is modulated to create an AC signalat the frequency of the line. In some embodiments, the AC voltagegenerator 110 generates the PWM signal to be amplified according withthe line frequency. In some variations, the PWM signal is generatedbased on a table. The table may be stored in the AC voltage generator110, for example, and the frequency generator of the AC voltagegenerator 110 generates the PWM signal by retrieving duty cycle valuesfrom a table at a rate of the determined line frequency.

Next, method 1000 continues with enabling the amplifier (step 1018).According to several embodiments, the AC voltage generator 110 of FIG. 4enables the amplifier 444 to begin amplifying the generated PWM signal.In some embodiments, the method 1000 optionally continues with adjustingthe generated PWM signal according to feedback (step 1020). The feedbackmay be from the output signal 116 applied to the irrigation controller106. By way of example, the AC signal may be maintained at a relativelyconstant 24 VAC and relatively free of distortion. This constancy andlack of distortion can be maintained despite variations in the load(i.e., electrical needs of the irrigation controller 106). In this case,the AC voltage generator 110 adjusts the generated PWM signal accordingto feedback received.

Next, method 1000 continues with determining if there is an over current(step 1022). And, if an over current is detected, the amplifier isdisabled (step 1012). In some embodiments, the current sensor 608 isconfigured to continually monitor the current, and upon detecting anover current, notifies the AC voltage generator 110 to disable theamplifier 444. Additionally and/or alternatively, method 1000 providesfor determining if there is a missing of a zero crossing (step 1024).According to some embodiments, the AC zero-crossing detector 606continually monitors the input AC voltage zero-crossings, wherein upondetecting a predefined number of missed zero crossings, the AC voltagegenerator 110 disables the amplifier 444.

Referring next to FIG. 11, a flow diagram of the steps performed in astart-up method for providing power for use by an irrigation controlleraccording to one embodiment. Method 1100 begins with determining theline frequency of the input AC voltage (step 1110). As described above,in some embodiments, the input AC voltage 102 is supplied to the ACzero-crossing detector in order to determine the frequency of the inputAC voltage 102. Next, the method 1100 continues with determining if theline frequency is above 56 Hz (step 1112). As described above inreference to FIG. 10, the AC voltage generator 110 may generate the PWMsignal to be amplified based on a table stored within the AC voltagegenerator 110. In some variations, the table comprises data points of asine wave, wherein the data points of the sine wave are fetched at apredetermined frequency in order to generate the PWM signal to beamplified. In the case that the line frequency is greater than 56 Hz,then method 1100 continues with updating the fetch frequency of the sinewave table values to generate an output AC voltage at 60 Hz. If the linefrequency is not greater than 56 Hz, then method 1100 continues todetermine if the line frequency is less than 54 Hz (step 1116). If theline frequency is less than 54 Hz, then method 1100 continues withupdating the fetch frequency of the sine wave table values to generatean output AC voltage at 50 Hz (step 1118).

In other variations, the AC voltage generator may be configured togenerate the output AC voltage 116 to be one of 50 Hertz (Hz) when afrequency of the input AC voltage is within a first frequency range and60 Hz when the frequency of the input AC voltage is within a secondfrequency range. For example, the first frequency range may be below 55Hz and the second frequency range may be 55 Hz and higher; or, forexample, the first frequency range may be 47 to 54 Hz, and the secondfrequency range may be 56 to 63 Hz.

Referring next to FIG. 12 a block diagram of components of the ACvoltage generator according to one embodiment is illustrated. The system1200 comprises a microcontroller unit 1210, a class D amplifier 1230(generically referred to as a power amplifier 1230) and output ACvoltage 116 load terminals 1250.

The system 1200, in some embodiments, may represent the AC voltagegenerator as discussed in reference to FIGS. 1-11 above. According toseveral embodiments, the microcontroller unit 1210 includes a currentsense input 1212, a sense voltage monitor 1214, and a zero-crossinginput 1216. The microcontroller unit 1210 further includes a power-upand/or enable output 1218, a first PWM output 1220, in some embodiments,a second PWM output 1222. The class D amplifier 1230 includes digitalinputs for a mode interface 1232 and a plurality ofcomparators/inverters 1234, and analog outputs from a plurality ofbridges 1236.

The first PWM output 1220 of the microcontroller unit 1210 is suppliedto one set of inputs, e.g., in1+ and IN2−, of the plurality ofcomparators 1234 of the class D amplifier 1230; and the second PWMoutput 1222 is supplied to the other set of inputs, e.g., in1− an IN2+,of the plurality of comparators 1234. The power-up and/or enable output1218 of the microcontroller unit 1210 is supplied to the mode interface1232 of the class D amplifier 1230. Additionally, a positive voltageVDD+ 1240 and a negative voltage VSS are supplied to the class Damplifier 1230. The output plurality of comparators 1234 are coupled tothe plurality of bridges 1236, wherein the outputs of the bridges 1236are fed back to the comparators 1234 in addition to supplying an outputAC voltage 116 to the output AC voltage load terminals 1250.

According to several embodiments, implementing an amplifier, such as theclass D amplifier 1230, takes advantage of this highly integratedsolution for benefits such as cost savings and reduced EMI. By way ofexample, the full bridge output structure of the class D amplifier 1230provides approximately 4 times more output power than the typicalamplifier, and, is thus highly efficient. Additionally, the full-bridgeoutput structure of the class D amplifier 1230 is fully differential,which provides additional EMI advantages. Therefore, the class Damplifier provides benefits of reduced size, cost and higher powerefficiency, making it an attractive choice for the power supply 104.

By way of example, the amplifier chosen for the power supply 104 maycomprise the following characteristics: analog or digital inputs,provisions for negative feedback, consequent power supply rejectionratio specifications, integrated or external output MOSFETS, distortionreduction scheme and implementation, output protection scheme andimplementation, output efficiency, high availability of complements andreduced electromagnetic interference generation.

In some variations in the present embodiment, the microcontroller unit1210 may comprise analog to digital converter. The analog to digitalconverter may be used, for example, to sample the input AC voltage tomeasure the time between the zero crossings. This measurement may beused to obtain the input frequency of the input AC voltage, and thus,output a PWM signal based on the input frequency. Additionally and/oralternatively, the analog to digital converter may be used to sample thepower supply 104's output AC voltage and determine if the poweramplifier may be enabled. Further, the analog digital converter may beused to sample and measure the output current in order to adjust the PWMoutput signal.

Now referring additionally to FIGS. 5 and 6, the current sense input1202, sense voltage monitor 1204 in the zero crossing input 1206 mayeach and input to an analog to digital converter in the microcontrollerunit 1210. The current sense input 1202 may receive a current, and/or acurrent signal from the monitor module 504 and/or current sensor 608. Insome variations, the microcontroller unit 1210 will monitor the outputcurrent, and, if at the load passes a predefined maximum threshold apredefined number of times, the microcontroller unit 1210 will shut downthe class D amplifier 1230 by sending a disabled signal. By way ofexample, if the load current is detected to pass an over current limitthree cycles in a row, the microcontroller unit 1210 will determine thisto be an unstable operating condition and will disable the amplifier.When an inductive load is powered for the first time, it produces aninrush current for two cycles; wherein, in the present embodiment, thisover current would not shut down the amplifier because it does notexceed over current limit three times in a row.

Similarly, the sense voltage monitor 1204 may receive a voltage, and/orvoltage level signal from the monitor module 504 and/or the currentsensor 608. In some embodiments, the current sense input 1202 and thesense voltage monitor 1204 may indicate to the microcontroller unit 1210that the power supply 104 is ready to begin generating an output ACvoltage. In some variations, this indication may occur when the currentsense input 1202 and the sense voltage monitor 1204 are each within apredefined threshold, indicating to the microcontroller unit 1210 thatthe AC to DC voltage converter has generated a sufficient voltage forthe class D amplifier to begin amplifying in the load current is withina stable operating condition.

This zero-crossing input 1206 may be supplied, for example, by themonitor module 504 and/or the zero-crossing detector 622. Thezero-crossing input 1206 may comprise a signal and/or a pulse for everyinstance the AC input voltage passes zero volts, for example.Additionally and/or alternatively, the zero-crossing input 1206 maycomprise a signal indicating to the microcontroller unit 1210 thefrequency of the input AC voltage. Additionally, the zero-crossing input1206 may indicate to the microcontroller unit 1210 that the input ACvoltage has missed crossing zero volts. In this case, if the input ACvoltage has missed crossing zero volts a predetermined number of times,the microcontroller unit 1210 may determine the input AC voltage isunstable and, thus, cause the AC voltage generator to cease generatingthe output AC voltage.

In some variations in the present embodiment, the microcontroller unit1210 may determine from their current sense input 1202, a sense voltagemonitor 1204 and zero crossing input 1206 at the power supply 104 isready to begin generating an output AC voltage. The microcontroller unit1210 may synchronize with the input AC voltage by waiting for the nextzero crossing of the input AC voltage. Additionally, the microcontrollerunit 1210 may samples the sense voltage monitor 1204 to determine thatthe DC voltage having been converted by the AC to DC voltage converterhas reached a predefine voltage, and thus, the amplifier may be enabled.After this determination has been made, the microcontroller unit 1210may send a power-up and/or enable signal to the mode interface 1232class D amplifier 1230. Additionally, the microcontroller unit 1210 mayreceive and/or determine the frequency of the input AC voltage via thezero crossing input 1206, wherein the frequency determines which PWMsignal will be generated.

In some variations, the microcontroller unit 1210 may store in memory aplurality of tables comprising values for generating PWM signals,wherein one of the plurality of tables is chosen depending on thefrequency of the input AC voltage. For example, the tables may containthe duty cycles for the PWM output to form a sine wave. In somevariations, the table may comprise the duty cycles for the PWM outputsto form only one quarter of a sine wave. Wherein, the values for onequarter of a sine wave are used by the microcontroller unit 1210 togenerate the rest of the values for the entire sine wave. Accordingly,the microcontroller unit 1210 will generate the first output PWM signal1220 and the second output PWM signal 1222 by fetching the table valuesfrom memory at a constant rate, wherein, the rate varies depending onthe input frequency of the input AC voltage.

The class D amplifier 1230, being digitally controlled, may beconfigured to amplify a periodic signal. Accordingly, the first outputPWM signal 1220 and the second output PWM signal 1222 received from themicrocontroller 1210 are amplified using the plurality of comparators1234 and the plurality of bridges 1236 in the class D amplifier. In someembodiments, the class D amplifier may provide efficiency of up to 87%over the full frequency range, wherein amplifier is well-suited todynamic power limiting without loss of efficiency. The external clockinput and logic control of operational mode of the class D amplifier, insome embodiments, make it easily to integrate into a microprocessorcontrolled system. For example, on-chip remote start up sequencing,self-testing and output protection features well-suited for such asystem. Additionally, the class D amplifier offers a fully integratedpair of amplifiers per integrated circuit for a simple implementation ofthe full-bridge configuration. The silicon-on-insulator configuration ofthe class D amplifier permits a high clock rate and zero “dead time”switching, resulting in low distortion, and a high cutoff frequency inview of the small filter component size; and, thus provides reducedsensitivity to load impedance variations. The integrated outputprotection scheme provides a fast response f needed to prevent outputfailures in the damage.

Referring next to FIG. 13, a diagram illustrating various waveforms andsteps performed to determine a frequency for an output voltage for useby an irrigation controller according to one embodiment. The waveformsdepicted are an input AC voltage line signal, the PWM output signal, apower-up signal, and enable signal, and an output AC voltage signal.Referring additionally to FIGS. 10-12, in order for the microcontrollerunit 1210 to start generating PWM signal, the microcontroller unit 1210synchronizes with the input AC voltage by waiting for the input ACvoltage line to cross zero volts 1302. The microcontroller unit 1210then begins generating the PWM output 1304 and pulls the enable signalline high 1306. At the next zero-crossing of the input AC voltage linesignal 1308, the microcontroller unit 1210 generates a power-up pulse1310. Accordingly, the power amplifier 1230 is enabled and beginsamplifying the PWM output signal to generate the output AC voltage 1312.

The power supply 104 will continue to generate the output AC voltage,however, the microcontroller unit 1210 will continue to monitor hiszero-crossing the input AC voltage line, and detect when the input ACvoltage misses a zero-crossing 1314. In some embodiments, the powersupply 104 will incorporate shutdown mechanics, for example, and upondetecting a predefined maximum allowable missed zero-crossings, thepower supply 104 will gracefully shutdown. By way of example, in oneembodiment upon detecting three missed zero-crossings 1316, themicrocontroller unit 1210 pulls the enable signal low 1318 and ceasesgenerating the PWM output signal 1320. Accordingly, the amplifier isdisabled and ceases generating the output AC voltage 1322.

In some embodiments, the microcontroller unit 1210 is configured to waitfor a predefined number of zero-crossings 1324, e.g., sixzero-crossings, to return to generating the PWM output signal 1114 andpulling the enable signal high 1328. Accordingly, on the nextzero-crossing 1330 the power-up signal is sent 1332 thereby enabling theamplifier to return to generating the output AC voltage 1334.

Referring next to FIG. 14, a high level circuit diagram illustrating oneembodiment of the power supply of FIG. 1 according to one embodiment isillustrated. System 1400 illustrates an embodiment comprising the frontend board 602 and the back end board 604 as discussed in regards to FIG.6. The front end board 602 includes the AC to DC voltage converter 108comprising the rectifier 320, power factor correction module 322 and DCto DC converter 324, as discussed in regards to FIG. 3. In theillustrated embodiment, the rectifier 320 includes an EMI filter andbridge, the power factor correction module 322 includes a PFC and PWMflyback front end, and the DC to DC converter 324 includes a DC to DCswitching mode power supply. In some embodiments, the front end board602 further includes a DC regulator 1420, the AC zero-crossing detector606 and an opto-coupler 1430.

The back end board 604 includes a current monitor 624 (shown in FIG. 6),comprising a current and voltage monitor 1440; and the AC voltagegenerator 110 comprising a microcontroller unit 1210 and a class Damplifier 1230, as discussed in regards to FIG. 12, and an isolator 446and filter 448, as shown in FIG. 4. As illustrated in FIG. 14, an inputAC voltage is supplied to the universal AC input terminals 1410 of thefront end board 602. In some embodiments, the input AC voltage rangesfrom 90 to 260 VAC and is supplied to the AC to DC converter adapted tooutput a DC signal derived from the AC signal.

The input AC voltage 102 is supplied to the rectifier 320 and ACzero-crossing detector 606. The output of the AC zero-crossing detector606 is supplied to the opto-coupler 1430, and the output of theopto-coupler 1430 is supplied to the microcontroller unit 1210 on theback end board 604. The output of the rectifier 320 is supplied to thepower factor correction module 322 prior to being supplied to the DC toDC converter 324. The output DC voltage signal 114, having beenconverted by the AC to DC voltage converter 108, in addition to beingsupplied to the back end board 604, is supplied to the DC regulator1430. In some embodiments, the DC voltage regulator 1430 generates aplurality of DC voltages 1460, e.g., VCC1 and VCC2, for use by one ormore components on the power supply 104 and/or to be supplied to theirrigation controller 106.

The output DC voltage signal 114 is supplied to the back end board 604by the AC to DC converter 108 on the front end board 602. The output DCvoltage signal 114 is supplied to the AC voltage generator 110 adaptedto generate an output AC voltage signal using the output DC voltagesignal 114 signal. Additionally, in some embodiments, a control outputis coupled to the AC voltage generator 110, wherein the control outputis adapted to couple to an irrigation control device, e.g., theirrigation controller 106; and the control output is further adapted todrive the irrigation control device with the output AC signal.

By way of example, the output DC voltage signal 114, having beenconverted, is supplied to at least the current sensor 608 and the classD amplifier 1230. In some embodiments, the current sensor 608 determinethe DC current of the output DC voltage signal 114, and supply the DCcurrent to the current to voltage monitor 1440. The output of thecurrent to voltage monitor 1440 is fed into the microcontroller unit1210, as discussed in regards to FIG. 12, in order to shut down the ACvoltage generator 110 in case of an overload. In some embodiments, thecurrent monitor 608 also divides the DC current in order to feed thecurrent to the microcontroller unit 1210, as discussed in regards toFIG. 12, to determine if the DC current is within a predetermined rangefor the stable operation of the power supply 104.

The front end board 602 also supplies the back end board 604 azero-crossing signal from the opto-coupler 1430. The zero-crossingsignal is supplied to the microcontroller unit 1210, as discussed inregards to FIG. 12, in order for the microcontroller unit 1210 to atleast synchronize with the input AC voltage. In some embodiments, thezero-crossing signal is also used to determine if a zero-crossing ismissed. According to several embodiments, the front end board 602supplies the plurality of DC voltages 1460, e.g., VCC1 and VCC2, to theback end board 604. For example, at least one of the plurality of DCvoltages 1460 is supplied to power at least some of the integratedcircuits on the back end board 604, such as, the microcontroller unit1210, the current to voltage monitor and/or the class D amplifier. Insome embodiments, at least one of the plurality of DC voltages 1460,VCC1 and VCC2, are supplied to the irrigation controller 106.

As described above in reference to FIG. 12, in some embodiments, oncethe input AC voltage is supplied to the universal AC inputs 1410, themicrocontroller unit 1210 determines if the power supply 104 is ready tostart generating power. Once ready, the microcontroller unit 1210determines the input frequency of the input AC voltage and synchronizeswith the input AC voltage at the next zero-crossing. The microcontrollerunit 1210 selects a table corresponding to the input frequency in orderto generate PWM signals on the PWM output lines (e.g., 1220 and 1222 inFIG. 12). The microcontroller unit 1210 will then enable the class Damplifier 1230 and send a power-up signal for the class D amplifier 1230to begin amplifying the PWM signal. After amplifying the PWM signals,the output of the class D amplifier 1230 is passed through the isolator446 and filtered through filter 448 prior to supplying the output ACvoltage to the irrigation controller 106 coupled to the output terminals1250 (which may be generically referred to as an output).

In some embodiments, the isolator 446 comprises a planar transformerconfigured to isolate the output of the AC voltage generator, e.g., theoutput of the class D amplifier 1230, and transform the amplifiedperiodic signal in order to generate the output AC voltage. In someembodiments, the power supply 104 requires the galvanic isolation, whichmay be achieved with a small transformer than in a traditional step-downpower supply. For such embodiments, a planar distribution transformermay be designed with the following characteristics: full power, fullbandwidth, 150 Wrms and 20 Hz to 200 Hz. By way of example, in someembodiments this design is implemented with the best available cores andPCB winding techniques to achieve the above performance levels.

The use of switching power supply technology, type D amplifiers,microcontrollers, and power-factor correction are all part of thesolution to the above problems. Also, the use of planar transformerswill significantly reduce the impact of the cost of copper. Becausethese technologies depend on the cost of electronic components, theremay be a tendency to decrease costs and increase their reliability overtime as the components become commodities. Electronic components alsoincrease their functionality and diversify capacities through time; thismay promote part consolidation because a generic functional layout maybe used for different applications by changing modular components.

In some embodiments, the above topologies for providing power to anirrigation controller are sufficient in systems with high power-on surgecurrents, and they provide good line regulation, load regulation andbrownout tolerance. This allows the class D amplifier 1230 to operatereliably, with an input power source ranging from 85 to 260 volts AC, at50 or 60 Hz. The power supply 104 may operate at rated power to deliver26.5 VAC±1 V, at 50 or 60 Hz, depending on the input frequency, anddeliver greater than 100 Watts.

Additionally, the above described topologies may be able to cope with agreat variety of load characteristics, including overload, short andopen circuit conditions. The power supply 104 may be able to deliverfull rated power for inductive loads. By way of example, this topologyis a viable commercial product because it is able to tolerate a greatestvariety of load characteristics and survive fault conditions, withoutdamaging sprinkler solenoids or other inductive loads. Additionally,these products are sold throughout the world, and the above describeddesigns may comply with a great variety of safety and quality standardsand certifications for multiple countries.

Many of the functional units described in this specification have beenlabeled as modules, in order to more particularly emphasize theirimplementation independence. For example, a module may be implemented asa hardware circuit comprising custom VLSI circuits or gate arrays,off-the-shelf semiconductors such as logic chips, transistors, or otherdiscrete components. A module may also be implemented in programmablehardware devices such as field programmable gate arrays, programmablearray logic, programmable logic devices or the like. It is also notedthat any of the components or modules of the various power suppliesdescribed herein may each alone or collectively be referred to as acircuit or circuitry.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions that may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the module and achieve the stated purposefor the module.

Indeed, a module of executable code could be a single instruction, ormany instructions, and may even be distributed over several differentcode segments, among different programs, and across several memorydevices. Similarly, operational data may be identified and illustratedherein within modules, and may be embodied in any suitable form andorganized within any suitable type of data structure. The operationaldata may be collected as a single data set, or may be distributed overdifferent locations including over different storage devices, and mayexist, at least partially, merely as electronic signals on a system ornetwork.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

Furthermore, the described features, structures, or characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. In the following description, numerous specific details areprovided, such as examples of programming, software modules, userselections, network transactions, database queries, database structures,hardware modules, hardware circuits, hardware chips, etc., to provide athorough understanding of embodiments of the invention. One skilled inthe relevant art will recognize, however, that the invention can bepracticed without one or more of the specific details, or with othermethods, components, materials, and so forth. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the invention.

While the invention herein disclosed has been described by means ofspecific embodiments, examples and applications thereof, numerousmodifications and variations could be made thereto by those skilled inthe art without departing from the scope of the invention set forth inthe claims.

1. An apparatus for providing power to an irrigation controller,comprising: an alternating current (AC) to direct current (DC) voltageconverter configured to convert an input AC voltage into a DC voltage;an AC voltage generator coupled to the AC to DC voltage converter, theAC voltage generator configured to generate an output AC voltage usingthe DC voltage; and the AC voltage generator coupled to the irrigationcontroller, the AC voltage generator further configured to supply theoutput AC voltage to the irrigation controller.
 2. The apparatus ofclaim 1, wherein the AC to DC voltage converter is further configured toconvert the input AC voltage having a voltage level at least within arange between 85 to 260 volts AC.
 3. The apparatus of claim 1, furthercomprising: a monitor module coupled to the AC to DC voltage converterand to the AC voltage generator, the monitor module configured to detectan unstable operating condition and cause the AC voltage generator tocease generating the output AC voltage.
 4. The apparatus of claim 1,further comprising: a current sensor coupled to the AC to DC voltageconverter, the current sensor configured to detect an input currentlevel.
 5. The apparatus of claim 1, further comprising: a zero-crossingdetector coupled to the AC voltage generator, the zero-crossing detectorconfigured to detect when the input AC voltage crosses zero volts. 6.The apparatus of claim 1, wherein the AC voltage generator comprises: afrequency generator configured to provide a frequency signal forgenerating the output AC voltage.
 7. The apparatus of claim 1, whereinthe AC voltage generator is further configured to generate the output ACvoltage at a substantially constant voltage and a substantially constantfrequency when the input AC voltage varies in at least one of frequencyand voltage level.
 8. The apparatus of claim 1, wherein the AC to DCvoltage converter further comprises a power factor correction module. 9.The apparatus of claim 1, wherein the AC voltage generator furthercomprises: a frequency generator configured to generate a pulse widthmodulated signal for generating the output AC voltage.
 10. The apparatusof claim 9, wherein the signal generator generates the pulse widthmodulated signal by retrieving duty cycle values from a table at a ratedependent on the frequency of the input AC voltage.
 11. The apparatus ofclaim 1, wherein the AC voltage generator further comprises: anamplifier configured to amplify a periodic signal using the DC voltagefor generating the output AC voltage.
 12. The apparatus of claim 11,wherein the amplifier further comprises: a class D amplifier.
 13. Theapparatus of claim 1, wherein the amplifier is a digitally controlledamplifier coupled to the AC to DC voltage converter, the digitallycontrolled amplifier configured to amplify the periodic signal when theDC voltage reaches a predefined threshold.
 14. The apparatus of claim 1,wherein the AC voltage generator further comprises: a planar transformerconfigured to isolate the output AC voltage and transform a periodicsignal used to generate the output AC voltage.
 15. The apparatus ofclaim 1, wherein the output AC voltage is used by the irrigationcontroller to actuate irrigation control devices.
 16. The apparatus ofclaim 1, wherein the AC voltage generator is further configured togenerate the output AC voltage to be one of 50 Hertz (Hz) when afrequency of the input AC voltage is within a first frequency range and60 Hz when the frequency of the input AC voltage is within a secondfrequency range.
 17. The apparatus of claim 16, wherein the firstfrequency range is below 55 Hz and the second frequency range is 55 Hzand higher.
 18. The apparatus of claim 1, wherein the AC to DC voltageconverter and the AC voltage generator are internal to a housing of theirrigation controller.
 19. The apparatus of claim 1, wherein theirrigation controller is external to a power supply 104 housingcontaining the AC to DC voltage converter and the AC voltage generator.20. A method for powering an irrigation controller comprising:converting an input alternating current (AC) voltage signal into adirect current (DC) voltage signal; generating an output AC voltagesignal using the DC voltage signal, the output voltage signal configuredto power the irrigation controller; and supplying the output AC voltageto the irrigation controller.
 21. The method of claim 20, wherein theconverting step further comprises: converting an input AC voltage signalhaving a voltage level at least within a range between 85 to 260 voltsAC.
 22. The method of claim 20, further comprising: monitoring the inputAC voltage and the DC voltage signal and ceasing generating the outputAC voltage upon detecting an unstable operating condition.
 23. Themethod of claim 20, further comprising: monitoring a current draw andceasing generating the output AC voltage when the current draw is abovea predefined threshold.
 24. The method of claim 20, further comprising:detecting when the input AC voltage signal crosses zero volts.
 25. Themethod of claim 20, wherein the generating step further comprises:generating a frequency based on a frequency of the input AC voltagesignal.
 26. The method of claim 20, wherein the generating step furthercomprises: generating the output AC voltage signal at a substantiallyconstant voltage and a substantially constant frequency when the inputAC voltage varies in at least one of frequency and voltage level. 27.The method of claim 20, wherein the converting step further comprises:correcting at least one of a frequency of an input AC current and aphase of the input AC current according to a frequency of the input ACvoltage and a phase of the input AC voltage.
 28. The method of claim 20,wherein the generating step further comprises: generating a pulse widthmodulated signal for generating the output AC voltage.
 29. The method ofclaim 28, wherein the generating a pulse width modulated signal stepcomprises retrieving duty cycle values from a table at a rate dependenton the frequency of the input AC voltage.
 30. The method of claim 20,wherein the generating step further comprises: amplifying a periodicsignal for generating the output AC voltage when the DC voltage reachesa predefined threshold.
 31. The method of claim 20, further comprising:actuating irrigating control devices using the output AC voltage havingbeen supplied to the irrigation controller.
 32. The method of claim 20,wherein the generating step further comprises: generating a frequency ofthe output AC voltage to be one of 50 Hertz (Hz) when a frequency of theinput AC voltage is within a first frequency and 60 Hz when thefrequency of the input AC voltage is within a second frequency range.33. The method of claim 32, wherein the first frequency range is below55 Hz and the second frequency range is 55 Hz and higher.
 34. A powersupply, comprising: an input configured to receive an input alternatingcurrent (AC) voltage ranging from 85 volts AC to 260 volts AC; an outputconfigured to couple to an irrigation device; and a circuit configuredto generate an output AC voltage; wherein the output AC voltage powersthe irrigation device and the output AC voltage is substantiallyconstant regardless of whether the input AC voltage varies in at leastone of frequency and voltage.
 35. The power supply of claim 34, whereinthe circuit is further configured to generate a frequency for the outputAC voltage to be one of 50 Hz when a frequency of the input AC voltageis within a first frequency range and 60 Hz when the frequency of theinput AC voltage is within a second frequency range.
 36. The powersupply of claim 34 further comprising: a voltage converter coupled tothe input configured to convert the input AC voltage to a direct current(DC) voltage; and wherein the circuit comprises a frequency generatorcoupled to an amplifier, the amplifier coupled to the voltage converter;wherein the frequency generator generates a periodic signal and theamplifier produces the output AC voltage using the DC voltage and theperiodic signal.
 37. The power supply of claim 34 further comprising amonitor coupled to the generator, the monitor configured to disable theamplifier upon detecting an unstable operating condition.
 38. A method,comprising: receiving an input alternating current (AC) voltage having avoltage level ranging between 85 to 260 volts AC; and generating, basedat least in part on the input AC voltage, a substantially constantoutput AC voltage configured to be used by an irrigation controllerregardless of whether the input AC voltage varies in at least one offrequency and voltage.
 39. The method of claim 38, wherein thegenerating step further comprises: producing a pulse width modulatedsignal by retrieving duty cycle values from a table at a rate dependenton the frequency of the input AC voltage.
 40. The method of claim 38,wherein the generating step further comprises: digitally controlling anamplification of a periodic signal to create the output AC voltage upondetecting the DC voltage is above a predefined threshold.
 41. Anirrigation controller power supply, comprising: an input adapted toreceive an alternating current (AC) signal; an AC to direct current (DC)converter coupled to the input, the AC to DC converter adapted to outputa DC signal derived from the AC signal; an AC generator adapted togenerate an output AC signal using the DC signal; a control outputcoupled to the AC generator, the control output adapted to couple to anirrigation control device; and the control output further adapted todrive the irrigation control device with the output AC signal.